Computer networks enable computers to communicate with each other and share data and information.
Hardware devices
Network Interface Card (NIC)
Any computer that is connected to a network, needs to have NIC. But, some computers such as laptops, they have two kinds of NIC. One for wired connections and another for wireless connections.
Hubs and switches
A hub is a device that connects a number of computers together to make a LAN (Local Area Network) If it receives a message, it sends to every computers in that network. Which means the networks are not secure as everyone can listen to communications. We can’t find hub anymore. A switch is a device that connects a number of computers together to make a LAN as the same as the hubs. But, the switches are better than the hubs. If it receives the message, it would check who it is addressed and send the information to the specific computer. Therefore, the switches are more secure than the hubs.
Bridges
A bridge is a network device that typically links together with two different parts of LAN.
Routers
A router is a network device that connects together with two or more networks. It’s mostly used to join a home or business network to the internet.
Wireless technology
Wireless technology allows the devices to connect to the network without the physical wires. It uses radio transmitter and receiver instead.
Network topologies
Star network
A computer or printer has a direct connection to a switch or hub then connect to a server. Its advantage is that even if one of those wire which is connecting to a device is damaged, the other devices still work.
Ring network
The devices are connected to one single wire. The information can only travel in one direction either clockwise or anti-clockwise. Its disadvantage is that if the wire is damaged, the other devices can’t work.
Bus network
All devices are connected to on main cable. At each end of the cable is a terminator, preventing signals from being reflected back.
Computer networks
Internet Service Providers (ISPs)
ISPs make home and business users to be able to connect to the internet.
Local Area Networks (LANs)
LAN is a network confined to one building or site. Which means that LANs are geographically small area. So, a LAN is a private network belonging to an organisation or business such as school. They usually use cables or wireless for the connections.
Types of LANs
There are two main types of LANs which are the client-server network and the peer-to-peer network.
A client-server network needs a server that is linked to a number of computers. It has fast process speed. There are three common types.
-File server : This can stores the files created and used by the organisation. All of the clients can access to the file by sending the commands.
-Database server :
-Print server : This does all the jobs from the computers which are connected to the server. Which means every single person’s don’t need to have their own printer.
A peer-to-peer network means that it doesn’t have any peripherals which are providing the specific jobs. Every devices are doing the same jobs. Every computers in a network can directly communicate with the other computers, unless they are on the network. Also, if the network has more than 10 computers, the access speed would be extremely slow.
Advantages and disadvantages of LANs compared with stand-alone computers
| Advantages | Disadvantages |
| -Data and software can be shared among-Software licenses can be less expensive rather than buying the software licenses for each of the people-Users can share printer and the other peripherals-Able to work together on the same document-Computers can be maintained remotely | -Viruses brought into one computer can be spread quickly across the network-Setting the LAN is much more expensive than setting the stand-alone computer-If the main server breaks, all the other computers on the network would stop working-Passwords may not be secure |
Wireless Local Area Networks (WLANs)
WLAN is a LAN using radio that uses radio signals (wi-fi) without connecting the computers with the cables or wires.
There are five components that my needed to make the wireless connection possible :
-Wireless access point
-Wireless repeaters
-Network Internet Cards
-Boosters (Amplifiers)
-Routers
Advantages and disadvantages of WLANs
| Advantages | Disadvantages |
| -Access to WLANs are more flexible than LANs -Users can access to the internet either indoor and outdoor -Wireless access point is also installed in the public areas |
-WLANs are slow if there are lots of computers connecting together -The distance of each computers connection is shorter than LANs |
Wide Area Networks (WANs)
WANs are several LANs are connected each other and make a WANs. It’s a network extended over a large area such as all around the world or all over a country or region. That’s why WANs are often used by the large companies which have the offices spread out all over the world. For WANs, often use optical fibre cables, satellite radio links, microwave radio links and high-speed telephone lines.
| Advantages | Disadvantages |
| -The organisations can share data quickly even though the distance is far -Transfer data is faster than any other methods |
-If telecommunication links fail, then communication across a WAN would not be possible -Viruses can spread very quickly through the networks -Hackers are more likely to attack the servers than LANs |
Internet is International Network
Internet provides open access to many areas of internet and it’s difficult to make secure as the people all around the world can see and access to it.
Intranet is Internal Restricted Access Network
Intranets are mostly used by the organisations or schools. Not everyone can access to intranet. Only the certain users can access with the password.
Advantages and disadvantages of intranet
| Advantages | Disadvantages |
| -Data is relevant to the users -Communication and searching speed is faster as its small size -More likely to be safe and appropriate |
-Limited access to customers and other organisations -Expensive to set up and maintain- |
Websites
The internet is made up of millions of websites and webpages.
Each webpage has an address which is known as URL Uniform Resource Locator
http://www.hapercollins.co.uk/about-hapercollins/Pages/about-us.aspx
| Protocol | Host name | Domain name | File path | Filename | ||
| (SLD) Second Level Domain | Sub domain | (TLD) Top Level Domain | ||||
| http:// | www | .hapercollins | .co | .uk/ | about-hapercollins/pages/ | about-us.aspx |
http or https are protocol.
HTTP : Hyper Text Transfer Protocol
HTTPS : Hyper Text Transfer Protocol Secure
HTTPS are mostly used for the websites which need to protect the people’s personal information.
Accessing the internet
| Method of internet access | Equipment required | Advantages | Disadvantages |
| Dial-up | Dial-up modem | -Cheap -Requires access to a telephone line |
-Slowest connection (56 kbps) -Telephone line tied up while the modem is in use |
| Cable | Cable modem | -Very fast, stable connection -Rapid access to movie and music downloads |
-It’s often only available in cities (not in the countryside) |
| Broadband | ADSL modem | -Fast connection -Fast access speed |
-Download and upload is limited |
The internet and networks
For multiple users on a network to access the same internet connection, a proxy server is needed. A proxy server acts as a gateway between network users.
The proxy server :
-submits just one request for all the users to the router
-can also store copies of webpages for easy access
-restricts access to some users
-checks the source or destination of a data packet and allows or refuses access
Batch processing
When a number of jobs gathering and send to the server and work at the same time. The organisations such as ; service providers, mail order companies or others would use batch processing. Also, it’s likely to produce a large amount of the data for the monthly pay bills and letters.
Online processing
It provides the users or customers to a network and allow to edit the data. It is often used by the booking the flight tickets, booking theatre or others. It provides the most recent data but it might be slower about couple of seconds.
Real-time processing
When an immediate response is needed. It’s mostly used for air traffic control, ATMs, medical monitoring equipment. It has really immediate reaction. (Faster than online processing) Therefore, it’s expensive.
Networks in financing
-Payments
-Invoicing
-Orders
-Payroll
-Banking
Payroll
The payroll system calculates wages, prints wage slips and send the data to the banking. So that the wages directly go to the employees’ bank account.
Input Output
-Employees’ personal data -Updated employees’ personal data
-Tax Payroll system -Management report
-Timesheets -Print payslip
-Banking (BACs) -Banking (BACs)
School management systems
Booking systems
| Advantages | Disadvantages |
| -The customers can pay via online -Don’t have to visit the certain place to book |
-The people who can’t access to the internet might be unable to use the online booking system -If an internet or system problem occurs during booking would cause duplicate, cancel or double bookings |
An example of booking system : a person who wants to book a hotel
1. Choose a hotel he wants to go
2. Choose the date he wants to visit
3. Choose the type of room he wants to stay at
4. Enter the personal information
5. Select the payment method
6. Prints the voucher
7. Go to the hotel and use the payment card
Computer networks in business environment
Banking applications : EFT (Electronic Funds Transfer). ATMs for cash withdrawals and bill paying, credit/debit cards, cheque clearing, phone banking and internet banking.
Medical applications : Doctors’ information systems, hospital and pharmacy record, monitoring and expert systems for diagnosis
Library applications : Such as records books and borrowers and the issue of books
Expert systems : In mineral prospecting, car engine fault diagnosis, medical diagnosis, chess games
A back branch will have its own LAN, where ATMs terminals at each counter and office computers will all connect with the file server. Each LAN will connect to the WAN.
Processing in ATMs
1. Insert the card into the ATM. Once a customer inserts the card into the ATM, the data from magnetic stripe or embedded chip would be read and a customer would be offered to choose the language option.
2. Enter the PIN number. Card would be checked whether that card digits exit or PIN number is correct.
3.Choose the options among the transaction, see balance, withdraw money or deposit.
- Select the amount of money.5. Get the money (if necessary) and get the receipt (if you prefer) and get the card back.Advantages and disadvantages of banking system
| Advantages | Disadvantages |
| -Money can be moved quickly between the accounts -See balance or transaction can be done from mobile |
-Not many bank branches are required (unemployment) -If can’t access to the electricity, the customers can’t do anything with ATMs -Fraud may take place. Because, if a person get the others’ card and unless they know a person’s PIN number, the people can easily withdraw the money |
The activities I’ve done about medical system and library system
Library system
A server in a library contains the data of all the books in a library and personal information about library members.
There are three ways to access to the information :
-magnetic stipes
-chips
-thumbprints
Process in a library
1. Scan the library member card to know whether a member would able to borrow books, any books a member needs to return or others. The message will be out to the librarian’s screen.
2. Scan the book that a member selected. So they can know the details about the book. On the screen, it will show the return date for a member.
Advantages and disadvantages of the library system
| Advantages | Disadvantages |
| -Books can be borrowed from the other libraries |
Expert system
Expert system is a piece of software programmed using artificial intelligence.
This is a diagram which is showing a simple expert system
User interface : an input screen where data is collected
Knowledge base : a database that contains data
Inference engines : software that use the rules to try to get the answers
Rules base : made up of inference rules that the inference can be used to answer the questions or tasks
Advantages and disadvantages of expert system
| Advantages | Disadvantages |
|
-Answers are always correct -All questions are answered |
-It’s expensive to set up and takes lots of time -Wrong data in knowledge base might be effect the accuracy of the answers |
An activity I’ve done about expert system
Methods of electronic communication
Instant Messaging
Video conferencing
Facsimile transmission
Blogs
Wikis
Tweets
Social networking
Telephone applications
Mobile telephones
Using the internet for phone calls
Securing the network
Passwords
Passwords needed to protect the data. The more complex and complicated passwords are more secure and less likely to be hacked.
Users IDs
Keeping your data confidential
All the data needs to be kept secure. There are some ways to keep the data secure.
Encryption
Encryption converts data into a code by scrambling it using by encryption key. It can only be unlocked with the certain key so that hackers can’t misuse the data.
Authentication techniques
Authentication techniques are used to identify users to a computer-based system or network.
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